[R-390] R-390 Antenna Relay Chatter

Fri Oct 7 16:13:04 EDT 2022

Like Jordan said...the voltages are pretty much the same. I would just replace it. The few pieces of tube gear I own all have a thermistor and 
am using a bucking transformer to provide 115 Volts AC.

Les

----- Original Message -----
From: Jordan Arndt <Outposter30 at shaw.ca>
To: Barry <n4buq at knology.net>, Les Locklear <leslocklear at hotmail.com>
Cc: R-390 Mailing List <r-390 at mailman.qth.net>
Sent: 10/7/2022 2:39:55 PM
Subject: Re: [R-390] R-390 Antenna Relay Chatter
________________________________________________________________________________

I stopped using "Stand By" on all my tube gear because the manner in which 
it is usually implemented allows the B+ voltages to soar, often beyond the 
rated voltages of caps and any other components exposed to the unloaded B+ 
voltage.

I also add a CL-90 thermistor in the AC line on all the tube gear I'd like 
to keep running. It drops the input AC by a few volts and provides an 
automatic soft-start. Just make sure there is some air circulation around 
the thermistor and that it's not too close to wiring and other heat 
sensitive parts, because they do give quite a bit of heat.

The 390 and 390A antenna relay circuit is pretty much the same, aside from 
the voltage IIRC, so the rectifier issues are also pretty much the same.

It sounds to me like your rectifier is in the process of failing. What 
happens when you use the Break In circuit...?  Does it chatter when 
operating in Break In mode also..?

73...Jordan VE6ZT

----- Original Message ----- 
From: "Barry" <n4buq at knology.net>
To: "Les Locklear" <leslocklear at hotmail.com>
Cc: "R-390 Mailing List" <r-390 at mailman.qth.net>
Sent: Friday, October 07, 2022 1:08 PM
Subject: Re: [R-390] R-390 Antenna Relay Chatter

> Hi Les,
>
> That advice appears to pertain to an R390A. This is an R390. Do you think 
> that would make any difference?
>
> BTW, I was using STANDBY primarily for warmup.
>
> Thanks,
> Barry - N4BUQ
>
>> From: "Les Locklear" <leslocklear at hotmail.com>
>> To: "David Wise" <d44617665 at hotmail.com>, "n4buq" <n4buq at knology.net>, 
>> "R-390
>> Mailing List" <r-390 at mailman.qth.net>
>> Sent: Friday, October 7, 2022 12:33:17 PM
>> Subject: Re: R-390 Antenna Relay Chatter
>
>> From the "Archives"
>
>> DO NOT use the "STANDBY" position on the FUNCTION switch. The now 
>> unloaded
>> stages will cause the various voltages in the receiver to rise upwards 
>> perhaps
>> beyond the tolerances of some critical components. This is caused by the
>> multiplicity error in our sometimes 120v+ line voltage v/s the 115v in 
>> use when
>> the 390A was designed and built. Since it is normal for the "LOCAL GAIN"
>> control to not completely mute the audio when turned down fully, it is 
>> natural
>> to consider putting the receiver in "STANDBY." Remember, DON'T. Instead, 
>> turn
>> the audio down and also back off the RF GAIN control to about 11 o'clock 
>> and
>> the residual audio will disappear and no damage will be done to the 
>> receiver.
>
>> Les Locklear
>
>> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on 
>> behalf of
>> David Wise <d44617665 at hotmail.com>
>> Sent: Friday, October 7, 2022 12:12 PM
>> To: Barry <n4buq at knology.net>; R-390 Mailing List <r-390 at mailman.qth.net>
>> Subject: Re: [R-390] R-390 Antenna Relay Chatter
>> Should not chatter. #1 suspect is CR801; selenium rectifiers have a 
>> notorious
>> habit of increasing forward resistance as they age. Convert to silicon 
>> plus a
>> resistor in series to mimic the natural forward resistance of new 
>> selenium. (I
>> don't know what that value should be.) This is what Tektronix did with 
>> their
>> oscilloscopes; for every selenium-powered model, they created a silicon
>> retrofit kit. One of my scopes has one.
>
>> Or you can add a reservoir capacitor, starting small and increasing until 
>> the
>> chatter is reliably gone at low mains voltage. I am using 100uF. Upside 
>> is
>> potentially reduced hum. Downside is that CR801 will continue to 
>> deteriorate,
>> so eventually the problem will recur.
>
>> HTH,
>> Dave Wise
>> SWL (inactive)
>> ________________________________
>> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on 
>> behalf of
>> Barry <n4buq at knology.net>
>> Sent: Friday, October 7, 2022 9:59 AM
>> To: R-390 Mailing List <r-390 at mailman.qth.net>
>> Subject: [R-390] R-390 Antenna Relay Chatter
>
>> When in STANDBY, the antenna relay in my R-390 produces a bit of chatter. 
>> Is
>> this normal? I see where that relay is fed, unfiltered, from CR801 which, 
>> from
>> the pictures in the manual, appear to be a stack of selenium diodes and 
>> I'm
>> wondering if that rectifier stack might be a problem. Anyone know what to
>> expect from that relay in STANDBY and, perhaps, what I'm seeing might be
>> normal?
>
>> Thanks,
>> Barry - N4BUQ
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